The lines of your coloring page are the rules you need to share with your team, share with them the boundaries. They are more likely to stay with in the lines if they know that they exist. Next by holding the work up for group and team acceptance they become their own self policing force. They can set self expectations and make constructive self criticism as well. The reward is acceptance and recognition from the team, an old saying is that a person can starve without any feedback, but only needs one good compliment to be filled to overflowing.
I was picking out some coloring books for my friends children when she informed me that she would like to get a couple of books too. This is a 30 something year old woman. She then began picking out colored pencils as well with a gleam in her eye like a kid in a candy store. She couldnt wait to get home and start coloring in her new books. She picked Barbie Doll, princess type books and methodically chose what colors she would use for the first picture.
Coloring books generally have a theme of sorts. It might be that they are based on a Disney movie, or it is about animals, or vehicles, or something else. When selecting books for your children, remember that they will want to express their creativity, and will have a lot of fun with any coloring book, but will be more interested in a coloring booklet with a theme that appeals to them. Choose a color book that features their favorite characters, or the item of interest in their life. For example, if your little boy just loves trains, get a Thomas the Train coloring book. If your little girl is as girly as they come, look for the Disney Princess coloring book, or possibly Strawberry Shortcake.